Staphylococcus aureus is a medically important human pathogen that is found in the nasal passages of approximately 1/3 of the human population. The nose serves as a reservoir for spread of this pathogen and predisposes the host to potential infection. Despite the importance of S. aureus to human health, molecular mechanisms and host factors influencing nasal colonization are not well understood. We have recently discovered an extracellular amyloid fiber produced by S. aureus during nasal colonization. This finding is extremely novel and exciting as S. aureus has never been shown to produce extracellular structures. We hypothesize that this extracellular fiber is important for S. aureus nasal colonization and persistence within the nose. Our preliminary results suggest that the fibers contribute to biofilm development and consist of multiple toxins, which are folding into beta sheet rich confirmations to self-assemble into amyloid fibers. The aims of this proposal will determine the composition, formation, degradation and role of S. aureus fibers during nasal colonization and biofilm development. At the conclusion of these studies, we will have expanded our knowledge of S. aureus nasal colonization and characterized a novel extracellular structure produced by this important commensal and pathogen.